Problems involved in maintaining a consistent density of sprayed liquid from a vehicle have long been recognized. For example, in a vehicular sprayer of the type having a number of spray heads and a pump for pumping liquid to the spray heads, it has been the practice to manually preset either the pump speed or the spray head pressure for a particular vehicle speed for operation only at that particular speed. However, it is not convenient or even possible to maintain a precise vehicular speed during spraying.
There are numerous applications in which it is necessary to continuously control the dissemination of a fluid from a reservoir, through control of the fluid pump motor speed. There are, for example, numerous agricultural and contracting operations in which tank trucks are used to selectively spray a liquid along particular paths where the liquid may produce some beneficial results. Other vehicles, for, example, crop dusting planes and fire fighting planes, need an accurate system for control of fluid flow to insure effectiveness and avoid waste. In existing systems the fluid being applied is controlled by manual operation of on/off switches and a timer device (for intermittent application). In these controls, the speed of the water pump is determined by the rpm of the delivery vehicle's engine.
Selective control of the flow rate is often necessary to meet certain environmental concerns, minimize wastage of fluid, or to minimize the time required to carry out the operation of applying the fluid. It is desirable that the flow rate be easily controllable by a single operator from a central location, as in the cab of the spray vehicle. It is also desirable to control the flow evenly in relation to ground speed regardless of change in speed or change in engine rpm of the vehicle that is applying the fluid. It is further advantageous to be able to easily change the dispensing rate after an initial setup of the control system. In addition, it is desirable to have automatically controlled intermittent application option for dispensing fluid at intervals determined by user input.